Hitherto, relay devices that transmit and receive (relay) data to and from a plurality of electronic control units (ECUs) connected to a bus have been used (see Patent Document 1, for example). Here, a bus is a subsystem that transfers data between components inside a computer or between computers, for example.
In a configuration in which not only a legal operator but also a large number of unspecified third parties can connect a tool (operation device) to the bus, however, it is conceivable that a malicious third party may connect an illegal tool to the bus to perform an illegal operation such as illegally reading data from an ECU connected to the bus or illegally rewriting a control program for an ECU connected to the bus. Under such circumstances, it is desired to take defensive measures against connection of an illegal tool to the bus.
[Patent Document 1] JP-A-2007-166302 corresponding to US 2007/0133578